A Comparison of Contrast and Sensitivity in Tc-99m Thyroid Scintigraphy between Nine Nuclear Medicine Centres of a geographic area

Purpose: To compare with Picker’s thyroid phantom the contrast and the sensitivity obtained with ten cameras used for Tc-99m thyroid scintigraphy in a geographic area.
Methods: The phantom image was acquired with the collimator and the acquisition parameters used in clinical practice. Contrast for the 12 mm hot (H12) and for the 9 and 12 mm cold (C9, C12) nodules was measured, as well as sensitivity (S in cp/MBq/s).
Results: Measured minimum-maximum values were as follows. Pinhole cameras (6): S = 62-131; H12 = 0.66-0.77; C12 = 0.77-0.90; C9 = 0.59-0.76. Non-pinhole cameras (4): S = 55-85; H12 = 0.52-0.59; C12 = 0.62-0.75; C9 = 0.30-50.
Conclusions: The pinhole collimators outclass the parallel hole ones in contrast. The sensitivity was the highest (S > 96) for five of the six pinhole collimators. As a direct consequence of this study, two centres decided to switch to pinhole collimator for thyroid scintigraphy.